I've been experimenting today with Vti based configuration and run into a few problems.

My head end is a Gentoo Linux box running up to date versions of tools and running libreswan-git as of today. The box is a Linode VM with a public IPv4 and IPv6 address. The VM is running a Linux 4.7.3 kernel.

lightning pluto # ip -V
ip utility, iproute2-ss160808
lightning pluto #

The client side is a Cisco IOS router running 16.6(3)M.

On the Cisco side I've got a working config already running for an IPSec connection to another appliance (a Palo Alto firewall). It is only the connection to the Libreswan box that I am having problems with and it looks like the problems are all Libreswan specific.

1. The first problem is when the IPSec completes negotiation. As soon as the IPsec connects up, I lose all IPv4 access to the remote box. This is made even worse because the public route to the client is also wiped out, so the IPsec session basically kills the connectivity to the box including that of the IPsec session due to a recursive routing loop and more specific /1's for the global routing table:

lightning ~ # ip route dev vti01  scope link  src  mtu 1438
default via dev eth0  metric 3 dev lo  scope host via dev lo dev vti01  scope link  src  mtu 1438 dev eth0  proto kernel  scope link  src
lightning ~ #

Even with: vti-routing=no I still see these routes appear, and experience this problem.

2. What I would ideally like to do is have a tunnel interface on the Cisco, and number it with Ideally then on the Libreswan box I would set which would give me a proper traditional numbered link. I only need connectivity across the directly connected subnet (don't want or need any other routes to be reachable just yet - I'm NATting for this purpose in the meantime).

The Cisco insists on as the src and dst proxy IDs for these sorts of VTI connections on it's side.

Using a /30 seems to be the most intuitive way from a routing perspective at least, but it's not obvious how to configure the /30 bearing in mind the 0/0 proxy-id requirement.

How would I configure Libreswan to work in this way? [This would allow me to match the config I have on the other IPsec Palo Alto head end, and consistency is a great thing!]

3. I am seeing packets leave the Cisco across the Cisco Tunnel interface, and I am seeing these packets enter the Libreswan vti. However every single one of them is being dropped:

lightning pluto # ifconfig vti01
vti01: flags=193<UP,RUNNING,NOARP>  mtu 1428
        tunnel   txqueuelen 1  (IPIP Tunnel)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 5257  dropped 5257  overruns 0  frame 0
        TX packets 2236  bytes 568568 (555.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lightning pluto #

The TX packets were from me doing pings from the head end. The Cisco never sees any packets input but sees lots of packets output.

Tested without iptables as well, so that isn't the issue.

What would cause this?

4. Possibly related to (3) are these two tunnel types actually the same?

22: vti01@NONE: <NOARP,UP,LOWER_UP> mtu 1428 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
    link/ipip brd

and on the Cisco:

router-2#show int tun 1
Tunnel1 is up, line protocol is up
  Hardware is Tunnel
  Description: Libreswan site-to-site IKEv2 VPN
  Internet address is
  MTU 17862 bytes, BW 256 Kbit/sec, DLY 50000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel linestate evaluation up
  Tunnel source (Cellular0), destination
   Tunnel Subblocks:
         Tunnel1 source tracking subblock associated with Cellular0
Set of tunnels with source Cellular0, 2 members (includes iterators), on interface <OK>
  Tunnel protocol/transport IPSEC/IP

So one is IP/IP and the other is IPSEC/IP.  Is this expected?

The libreswan config looks like this:

conn router-2.reub.net

A tcpdump output shows the same, ie lots of packets dropped by the interface with no obvious reason why.

Logs (ie pluto.log and from the Cisco) are very verbose, if there are of use then perhaps I can send through the relevant bits and pieces.

The ikev2 session is however up, so we're almost at a working state:

router-2# show crypto ikev2 session detailed
 IPv4 Crypto IKEv2 Session

Session-id:19, Status:UP-ACTIVE, IKE count:1, CHILD count:1

Tunnel-id Local Remote fvrf/ivrf Status 1 none/none READY Encr: AES-CBC, keysize: 256, PRF: SHA1, Hash: SHA96, DH Grp:5, Auth sign: PSK, Auth verify: PSK
      Life/Active Time: 86400/3850 sec
      CE id: 2585, Session-id: 19
      Status Description: Negotiation done
      Local spi: D92301DC166D08E1       Remote spi: B17833A6ED12E5C2
      Local id: route...@reub.net
      Remote id: lightning.reub.net
      Local req msg id:  255            Remote req msg id:  219
      Local next msg id: 255            Remote next msg id: 219
      Local req queued:  255            Remote req queued:  219
      Local window:      5              Remote window:      1
      DPD configured for 15 seconds, retry 2
      Fragmentation not  configured.
      Extended Authentication not configured.
      NAT-T is detected inside
      Cisco Trust Security SGT is disabled
      Initiator of SA : Yes
Child sa: local selector -
          remote selector -
          ESP spi in/out: 0xE6E04BB5/0x3D26C686
          AH spi in/out: 0x0/0x0
          CPI in/out: 0x0/0x0
          Encr: AES-CBC, keysize: 128, esp_hmac: SHA96
          ah_hmac: None, comp: IPCOMP_NONE, mode tunnel

 IPv6 Crypto IKEv2 Session


Any advice would be appreciated. I guess by using Cisco IOS and Gentoo Linux I am not running an entirely standard combination of client+server but nevertheless it would be good to be able to get this working, and to have Gentoo be a working OS with VTI.

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